ABSTRACT
The article is devoted to the control measures of the tax authority against the cases of tax reduction that occur during the fulfillment of the tax liability of the economic entity and the mechanism for detecting tax evasion. On this basis, in the assessment of quantitative and qualitative indicators, using the methodology of fuzzy logic IF–THEN, it is possible to increase the declared income only by increasing the fines without paying attention to the usefulness of the collection, or by increasing the usefulness of the collection without changing the fines. The article assumed that declared profitability, specific weight of the collected tax and the specific weight of income remaining at the disposal of a taxpayer were taken as fuzzy variables. However, the analysis shows that profitability differs both by fields and by taxpayers operating in each field. Therefore, the declared profitability factor and the penalty for its concealment should be treated differently.